Ron Pisarz, Jr.
My #1 suggestion is this: make the rushing variant an option. While it isn't the only variant I use, it's the most important and as far as I can tell is the most popular. I could live without my other variants but without rushing I just feel the game is too imbalanced in favor of Jack (I don't say this lightly, I've played 100+ times).
Without question the rush in variant is required. Our group uses this variant as well otherwise it is too easy for Jack. Borders on not playable without it.